There has been widely known a hydraulic valve timing adjusting device for adjusting a valve timing of an intake valve by the pressure of a working liquid. Generally, the hydraulic valve timing adjusting device is provided with a housing rotor and a vane rotor which rotate in conjunction with a crankshaft and a camshaft of the internal combustion engine, and when the vane rotor receives the pressure of the working liquid in the housing rotor, a rotation phase between these rotors is changed. As a result of the change in the rotation phase, a valve timing is adjusted.
Japanese Patent No. 4161356 discloses the following technique as a kind of hydraulic valve timing adjusting device: that is, in an internal combustion engine, assuming that a rotation phase advancing further than the most retarded phase is an intermediate phase, a rotation phase reaching the intermediate phase is locked at the time of starting the internal combustion engine. According to this locking function, a timing when the intake valve is closed is advanced as early as possible and hence an actual compression ratio in the cylinder is increased, so that the temperature of gas in the cylinder is increased by compression heating, which hence results in accelerating the vaporization of fuel. Hence, for example, at the time of cold starting of the internal combustion engine held unattended in the state where the internal combustion engine is stopped under a low temperature environment such as an extremely low temperature, startability can be ensured.
However, in the hydraulic valve timing adjusting device of Japanese Patent No. 4161356 in which an intake valve is closed at an early timing, a high actual compression ratio in the cylinder is likely to cause the following problems, for example, at the time of warm starting of the internal combustion engine under a comparative high temperature environment such as ordinary temperatures. One of the problems is the occurrence of knocking. Another problem is to cause a state of pre-ignition in which at the time of restarting the internal combustion engine applied to an idle stop system or a hybrid system or at the time of restarting just after stopping the engine by an ignition off, the temperature of gas when the gas is compressed in the cylinder becomes too high and hence the gas is ignited by itself before ignition. Still another problem is to cause uncomfortable vibrations and noises by increased variations in the cranking rotation caused by a large compressive reactive force.
Hence, in the hydraulic valve timing adjusting device disclosed in JP-2002-256910A, one of a retard phase and an intermediate phase advancing further than the retard phase is selected at the time of starting the internal combustion engine, the retard phase being a rotation phase for closing an intake valve at a timing later than a timing when a piston in a cylinder reaches a bottom dead center. According to this selection of the rotation phase, it is possible to realize starting suitable for the temperature of the internal combustion engine (hereinafter referred to as “engine temperature”)
However, in the hydraulic valve timing adjusting device disclosed in JP-2002-256910A, by applying the pressure of the working liquid to a vane rotor in a housing rotor at the time of warm starting of the internal combustion engine, a retard phase is selected not by locking but by adjusting the rotation phase. For this reason, at the time of starting when the pressure of the working liquid is decreased, the vane rotor is relatively rotated to an advance side with respect to the housing rotor by a varying torque applied thereto from a camshaft and hence the rotation phase is easily shifted from the retard phase.
Furthermore, in the hydraulic valve timing adjusting device disclosed in JP-2002-256910A, a change of the rotation phase to the intermediate phase is caused by the varying torque at the time of cold starting of the internal combustion engine, so that the working liquid for applying pressure to the vane rotor in the housing rotor is drained. As a result, the working liquid for applying pressure to a lock body is also drained, so that the lock body is moved to a lock releasing position, which makes it difficult to lock the rotation phase at the intermediate phase.